An investigation in June found "significant deficiencies", and ordered improvements to be introduced by October.

Inadequate historic records mean that the precise contents of Sellafield and Dounreay are unknown.

"Consequently, we have yet to choose the best way to retrieve the materials safely and without endangering the environment," NDA said.

Sir Anthony, speaking on BBC Radio 4's Today programme, highlighted the four operating Magnox stations - Dungeness in Kent, Oldbury in Gloucestershire, Sizewell in Suffolk and Wylfa in north Wales - which will all be closed by 2010.

Future generations

Current plans assume that after initial work for 10 or 15 years, the "more difficult pieces" are dealt with some 70 years later.

"That's leaving the problem for future generations and throughout that period you've got the problem of storage, safety, security," Sir Anthony said.

"We believe it ought to be possible to complete the decommissioning of these stations over a 25-year period."

During the consultation period, NDA staff will host and attend meetings to explain the document and answer questions, the NDA said.

A final strategy is expected to be published next spring.

Among issues that the authority is looking at is the need for an alternative for Drigg in Cumbria, which is the only place in the country where low-level nuclear waste can be stored in perpetuity.

Drigg is about 1km from a shoreline that is eroding at the rate of 1 metre a year.

'Huge risks'

There is a risk it could flood between 500 and 5,000 years after it is closed.

Former environment minister Michael Meacher expressed concern at the cost of the decommissioning and questioned plans for future nuclear builds.